This invention relates to the production of non-woven fiber webs, and more particularly to improved means for controlling the density of such webs. Even more particularly this invention relates to an improved web-forming condenser, and means for controlling the fiber web or mat formed thereby.
It is conventional to employ pneumatically-operated systems for supplying air-borne fibers to the feed chutes for carding machines and the like. As shown for example in U.S. Pat. No. 4,240,180, a vertically-disposed feed chute collects fibers from an overhead, pneumatic fiber supply system, and then forms the fibers into a continuous, non-woven fiber mat or web, which is fed from the lower end of the chute to the input of a carding machine. As disclosed in that particular patent, fibers are collected in the upper or surge section of the chute, and are fed by one or more feed rolls onto an opening roll, which rotates about a horizontal axis intermediate the ends of the chute. The opening roll feeds the fibers downwardly to a formation section of the chute, from where they pass onto the perforated surface of a condenser drum that rotates at the lower end of the chute to form a continuous fibrous mat or web which is fed to the associated carding machine.
With this type of apparatus it is particularly desirable to be able to control the uniformity and density of the mat or web produced at the lower end of the feed chute. As taught in the above-noted U.S. Pat. No. 4,240,180, one such control is effected by varying the speed of rotation of the feed rolls, so that the quantities of fibers fed thereby to the formation section of the chute will be increased or decreased, as necessary, in order to effect a corresponding increase or decrease in the density of the web produced at the output of the chute.
Although web density thus can be controlled by varying the rate at which fibers are fed to a condenser, it is desirable to provide means for producing a more responsive control of the web density--i.e., means which can effect a more instantaneous change in the density of the web that is being formed at the output of a fiber supply chute.
It is an object of this invention, therefore, to provide improved means for rapidly and accurately controlling the density of a web produced at the output of a fiber supply chute of the type described.
Another object of this invention is to provide improved means for sensing the density of a fiber web formed on a condenser at the output of a feed chute of the type described, and for effecting almost instantaneous changes in the density of the web to conform to a predetermined desired density.
A more specific object of this invention is to provide an improved type of condenser for use at the output of a feed chute of the type described, and associated means for mechanically compacting the web, as required, to provide a web of uniform, predetermined density.